A disaster(from Latin language (meaning, "bad star") is the impact of a natural disaster natural or man-made event that negatively affects life, property, livelihood or industry often resulting in permanent changes to human society, ecosystems and natural environment.
(Note that the event itself is not a disaster; it is the impact which is called a disaster.) Disasters manifest as hazards exacerbating vulnerable conditions and exceeding individuals' and communities' means to survive and thrive.
The word's roots imply that when the stars are in a bad position, a disaster is about to happen.
Natural Disasters
A Natural phenomenon can easily cause a natural disaster. Appearing to arise without direct human involvement, natural disasters are sometimes called an act of God. A natural disaster may become more severe because of human actions prior, during or after the disaster itself. A specific disaster may spawn different types of events and may reduce the survivability of the initial event. A classic example, is an earthquake that collapses homes, trapping people and breaking gas mains that then ignite, and burn people alive while trapped under debris. Human activity in risk areas may cause natural disasters.
Avalanche
An avalanche is a slippage of built-up snow down an incline, possibly mixed with ice, rock, soil or plant life in what is called a debris avalanche. Avalanches are categorized as either slab or powder avalanches. Avalanches are a major danger in the mountains during the winter as a large one can run for miles, and can create massive destruction of the lower forest and anything else in its path. For example, in Kashmir, Close to the Jawahar Tunnel, in 2004-05 winters huge avalanches blocked the national highway for quite some time endangering the lives of hundreds who were trapped in and around the tunnel .Another example is from France where in 1999, 300,000 cubic meters of snow slid on a 30 degree slope, achieving a speed of 100 km/h. It killed 12 people in their chalets under 100,000 tons of snow, 5 meters deep.
Cold
Every year our country faces severe cold waves. With the mercury approaching the freezing temperature, it not only disrupts normal living, but also costs hundreds of people their lives each year. With the cover of smog thickening each year the things are getting worse. The sensitization in this regard is still missing and therefore the problem is being dealt with in an ad-hoc manner.
Cyclone
A storm surge is an onshore rush of water associated with a low pressure weather system, typically a tropical cyclone. Storm surge is caused primarily by high winds pushing on the ocean's surface. The wind causes the water to pile up higher than the ordinary sea level. Storm surges are particularly damaging when they occur at the time of a high tide, combining the effects of the surge and the tide. The highest storm surge ever recorded was produced by the 1899 Bathurst Bay Hurricane, which caused a 13 m (43 feet) storm surge at Bathurst Bay, Australia. In the US, the greatest recorded storm surge was generated by Hurricane Katrina, which produced a storm surge of 9 m (30 feet).
Droughts
A drought is a long-lasting weather pattern consisting of dry conditions with very little or no precipitation. During this period, food and water supplies can run low, and other conditions, such as famine, can result. Droughts can last for several years and are particularly damaging in areas in which the residents depend on agriculture for survival. The recent Karnataka and Rajasthan droughts have caused extensive damage.
Earthquake
An earthquake is a sudden shift or movement in the tectonic plates in the Earth's crust On the surface, this is manifested by a moving and shaking of the ground, and can be massively damaging to poorly built structures. The most powerful earthquakes can destroy even the best built of structures. In addition, they can trigger secondary disasters, such as tsunamis and fires. Earthquakes occur along fault lines, and are unpredictable. They are capable of killing hundreds of thousands of people, such as in the Tangshan earthquake 1976 Tangshan and 2004 Indian Ocean earthquakes.
Epidemics
Disease becomes a disaster when it spreads in a pandemic or epidemic as a massive outbreak of an infectious agent. Disease is historically the most dangerous of all natural disasters. Different epidemics are caused by different diseases, and different epidemics have included the Black Death, smallpox, and AIDS. The Spanish flu of 1918 was the deadliest ever epidemic, it killed 25-40 million people. The Black Death, which occurred in the 14th Century, killed over 20 million people, one third of Europe's population. Plant and animal life may also be affected by disease epidemics and pandemics.At one point in time we had only a few known epidemics to face(eg. malaria,cholera and typhoid). As the carriers are becoming immune to the traditional chemicals that we use for disease control the problems are increasing. SARS, DROPSY,DENGUE,BIRD FLU to name a few, have come up in recent years. The combat strategies for these are still in incubation stage.
Famine
Famine is a natural disaster characterized by a widespread lack of food in a region, and can be characterized as a lack of agriculture foodstuffs, a lack of livestock, or a general lack of all foodstuffs required for basic nutrition and survival. Famine is almost always caused by pre-existing conditions, such as drought, but its effects may be exacerbated by social factors, such as war. Particularly devastating examples include the Ethiopian famine and the Irish Potato Famine
Fire
A fire is a natural disaster that may destroy ecosystems like grasslands, forests causing great loss of life, property, livestock and wildlife. Bush fires, forest fires and mine fires are generally started by lightning, but also by human negligence or arson, and can burn thousands of square kilometers. An example of a severe forest fire is the Kumaun forest fire about a decade back.
Flood
A flood is a natural disaster caused by too much rain or water in a location, and could be caused by many different sets of conditions. Floods can be caused by prolonged rainfall from a storm, including thunderstorms, rapid melting of large amounts of snow, or rivers which swell from excess precipitation upstream and cause widespread damage to areas downstream, or less frequently the bursting of man-made dams. A river which floods particularly often is the Huang He in China, and a particularly damaging flood was the Great Flood of 1993.
Hail
A hailstorm is a natural disaster where a thunderstorm produces a numerous amount of hailstones which damage the location in which they fall. Hailstorms can be especially devastating to farm fields, ruining crops and damaging equipment. A particularly damaging hailstorm hit Munich, Germany on August 31, 1986, felling thousands of trees and causing millions of dollars in insurance claims. Skeleton Lake was named so after 300-600 people were killed by a hailstorm.
Heat
A heat wave is a disaster characterized by heat which is considered extreme and unusual in the area in which it occurs. Heat waves are rare and require specific combinations of weather events to take place, and may include temperature inversions, catabolic winds, or other phenomena. The worst heat wave in recent history was the European Heat Wave of 2003
Hurricane
A hurricane is a low-pressure cyclonic storm system which forms over the oceans. It is caused by evaporated water which comes off of the ocean and becomes a storm. The Coriolis Effect causes the storms to spin, and a hurricane is declared when this spinning mass of storms attains a wind speed greater than 74 mph. In different parts of the world hurricanes are known as cyclones or typhoons. The former occur in the Indian Ocean, while the latter occur in the Eastern Pacific Ocean. The most damaging hurricane in the United States was Hurricane Katrina, which hit the United States Gulf Coast in 2005.
Impact Event
Impact events are caused by the collision of large meteoroids, asteroids or comets (generically: bolides) with Earth and may sometimes be followed by mass extinction of life. The magnitude of the disaster is inversely proportional to its rate of occurrence, because small impactors are much more numerous than large ones.
Landslide
A landslide is a disaster closely related to an avalanche, but instead of occurring with snow, it occurs involving actual elements of the ground, including rocks, trees, parts of houses, and anything else which may happen to be swept up. Landslides can be caused by earthquakes, volcanic eruptions, or general instability in the surrounding land. Mudslides, or mud flows, are a special case of landslides, in which heavy rainfall causes loose soil on steep terrain to collapse and slide downwards (see also Lahar); these occur with some regularity in parts of California after periods of heavy rain.
Mudslide
A mudslide is a slippage of mud because of poor drainage of rainfall through soil. An underlying cause is often deforestation or lack of vegetation. Some mudslides are massive and can decimate large areas. On January 10, 2005 at 1:20 pm in La Conchita, a massive mudslide buried four blocks of the town in over 30 feet of earth. Ten people were killed by the slide and 14 were injured. Of the 166 homes in the community, fifteen were destroyed and 16 more were tagged by the county as uninhabitable.
Solar Flare
A solar flare is a violent explosion in the Sun's atmosphere with an energy equivalent to tens of millions of hydrogen bombs. Solar flares take place in the solar corona and chromosphere, heating the gas to tens of millions of kelvins and accelerating electrons, protons and heavier ions to near the speed of light. They produce electromagnetic radiation across the spectrum at all wavelengths from long-wave radio signals to the shortest wavelength gamma rays. Solar flare emissions are a danger to orbiting satellites, manned space missions, communications systems, and power grid systems.
Thunderstorm
A thunderstorm is a form of severe weather characterized by the presence of lightning and its attendant thunder, often accompanied by copious rainfall, hail and on occasion snowfall and tornadoes.
Tornado
A tornado is a natural disaster resulting from a thunderstorm. Tornadoes are violent currents of wind. Tornadoes can occur one at a time, or can occur in large tornado outbreaks along a squall line. The most powerful tornado ever recorded in terms of wind speed was the tornado which swept through Moore, Oklahoma on May 3, 1999 and reached wind speeds of up to 318 mph
Tsunami
A tsunami is a giant wave of water which rolls into the shore of an area with a height of over 15 m (50 ft). It comes from Japanese words meaning harbor and wave. Tsunamis can be caused by undersea earthquakes as in the 2004 Indian Ocean Earthquake, or by landslides such as the one which occurred at Lituya Bay, Alaska. The tsunami generated by the 2004 Indian Ocean Earthquake currently ranks as the deadliest tsunami in recorded history.
Volcanic Eruption
This natural disaster is caused by the eruption of a volcano, and eruptions come in many forms. They range from daily small eruptions which occur in places like Kilauea, in Hawaii, or extremely infrequent super volcano eruptions in places like Lake Toba. Recent large volcanic eruptions include that of Mount St. Helens and Krakatoa, occurring in 1980 and 1883, respectively.
Winter Storm
A snowstorm is a winter storm in which the primary form of precipitation is snow. When such a storm is accompanied by winds above 32 mph that severely reduce visibility, it becomes a blizzard. Hazards from snowstorms and blizzards include traffic-related accidents, hypothermia for those unable to find shelter, as well as major disruptions to transportation and fuel and power distribution systems.
Man Made Disasters
Disasters having an element of human intent, negligence, error or involving a failure of a system are called man-made disasters. Man-made disasters like power or telecommunication outages may be caused by thunderstorms, tornados or earthquakes and though the root cause is a natural phenomenon, they are considered to be man-made disasters.
Aviation
Planes are either hijacked or they crash. Both lead to disasters. Plane crashes have killed many people inn the past.
Arsons
Arson is the criminal intent of setting a fire with intent to cause damage. The definition of arson was originally limited to setting fire to buildings, but was later expanded to include other objects, such as bridges, vehicles, and private property. Arson is the greatest cause of fires in data repositories.
CBRNs
A catch-all initials meaning Chemical Biological Radiological Nuclear. The term is used to describe a non-conventional terror threat that, if used by a nation, would be considered use of a weapon of mass destruction. This term is used primarily in the United Kingdom. Planning for a CBRN event may be appropriate for certain high-risk or high-value facilities and governments.
Civil Disorders
Civil disorder is a broad term that is typically used by law enforcement to describe one or more forms of disturbance. Examples of disastrous civil disorder include, but are not
necessarily limited to: riots; sabotage; and other forms of crime. Although civil disorder does not necessarily escalate to a disaster in all cases the event may escalate into general chaos.
There were riots in the Watts neighborhood of Los Angeles, California in 1968 and 1992. The 1992 riots which started at the Florence and Normandee intersection of Watts were started immediately after the Rodney King verdict was announced on live TV. About 50 people died in the 1992 riots.
Power Outage
A power outage is an interruption of normal sources of electrical power. Short-term power outages (up to a few hours) are common and have minor adverse effect, 
since most businesses and health facilities are prepared to deal with them. Extended power outages, however, can disrupt personal and business activities as well as medical and rescue services, leading to business losses and medical emergencies. Extended loss of power also interferes with law enforcement, creating opportunities for crime, including vandalism, looting, arson and violent crime, even leading to civil disorder, as in the New York City blackout of 1977.
Only very rarely do power outages escalate to disaster proportions, however, they often accompany other types of disasters, such as hurricanes and floods, which hampers relief efforts.
Radio Contamination
When nuclear weapons are detonated or nuclear containment systems are otherwise compromised, airborne radioactive particles (fallout) can scatter and irradiate large areas. Ionizing radiation is hazardous to living things, and in such a case much of the affected area could be unsafe for human habitation. The Soviet republics of Ukraine and Belarus are part of a scenario like this after a reactor at the Chernobyl nuclear power plant suffered a meltdown in 1986.
Train Accidents
Train accidents are not an un-common happening. But at times the magnitude is so large that it is referred to as a disaster.